For splicing ends of conveyor belts together, metal belt fasteners are commonly employed that are secured to the belt ends as by various types of attachment members such as staples, bolts, rivets, and the like. The metal fasteners can be either of the hinged variety wherein they include plates attached onto one belt end and having loops projecting from the belt end that mate with loops of hinge fasteners attached on the other belt end for receiving a hinge pin therethrough, or can be of the solid plate variety where the fasteners span the belt ends for being attached thereto and thus do not employ a hinge pin. In either instance, the metallic fasteners provide distinct splice points along the run of the conveyor belt system where conveyor components that engage the belt surfaces such as belt cleaners, rollers and the conveyed material itself chute fed onto the belt will impact a harder material than that of the belt material that they otherwise would normally engage. These impacts cause abrasion and wear of these engaging components and can lead to unsatisfactory performance and their premature failure, and can also generate environmental problems such as where the conveyed material, e.g. rocks, coal, sand, etc., is broken up into fine air-borne particles by being dropped onto the metallic splice.
Most conveyor belts have an elastomeric or PVC-type material in which carcass material is embedded for strength purposes so that the conveyor belt covers against which, for example, blades of the belt cleaners are biased for scraping their surfaces clean will transition at the splice from engaging the softer rubber or PVC belt covers to the harder metallic material of the splice fasteners. This engagement with the metallic splices can induce vibrations in the cleaner blade generating a condition called “chattering” of the cleaner which can cause excessive damage to the conveyor belts. Accordingly, there is a need for a conveyor belt fastener that reduces the deleterious effects of high impact forces with metallic splices in terms of excessive wear of conveyor components such as the above-described belt chattering problems and the environmental problems that can be caused by impacts of the conveyed material with the splice.
Another problem with the typical belt fasteners is the gap spacing provided between the distinct fasteners along a particular splice. These gaps provide spaces for material such as aggregate rock material to sift between the fasteners and below to the interface between the rollers and the lower surface of the conveyor belts as well as to the other drive mechanisms under the belt. Also, conveyed material can get stuck in these gaps where belt cleaners cannot reach the material such that it is carried back on the return run of the conveyor. With solid plate fasteners, the fasteners are typically individually applied to the belt ends via a template that provides them with an optimum spacing between each other so that the belt can trough at a desired angle along the sides thereof to keep the material on the belt from falling off the sides, as is known. Further, the spacing is selected so that the holes through the belt for the attachment members, e.g. such as bolts for the solid plate fasteners, are not so frequent so as to damage the belt integrity and create undue weakness therein. Accordingly, there is a need for a belt fastener that allows for belt troughing while still minimizing sifting and carry back of conveyed material between adjacent plates along a splice formed by the fasteners.
For the high force impact problem such as manifested in one example by blade chattering, applicants' assignee herein has employed a solid plate fasteners having individual upper plates thereof having a thin coat of an elastomeric material thereon. While this fastener is likely to better absorb the forces of impact between, for instance, the cleaner and the belt splice formed with these fasteners, they do little to address the sifting problem created by the gaps left between adjacent plates attached along the belt ends in the splice. Another shortcoming is the time needed to clean flashing from those plates having thin rubber coatings individually molded thereon.
U.S. Pat. No. 5,839,571 discloses a belt joining device having a general H-shape with two pairs of opposing flanges that are to be secured onto the respective belt ends for splicing the belts together via small embedded grommetted inserts for receiving attachment members that extend through the belt. This joining device generally uses conveyor belt-type material including rubber material having carcass reinforcement cables arranged in a pattern embedded in the material. Like a conveyor belt, it is these reinforcement cables that provide the H-joining device its strength, and thus the flanges generally are fairly thick to accommodate the cables extending therein for strength purposes and therefore are of a higher profile than desired.
Accordingly, while the joining device of the '571 patent accommodates troughing of the conveyor belt, it has been found that in practice it generates excessive chatter of the cleaning blade producing damage to the conveyor belt adjacent splice. The high profile creates high force impacts with the blade cleaner that tend to damage the joining device decreasing the life of the splice more rapidly than is desired. With the damage to the belt caused by the chatter of the blade adjacent to the splice, when the splice fails, the splice installer has to take out a greater amount of the belt including the adjacent damaged portion thereof for forming the new splice. In many conveyor belt systems, there is insufficient belt length on the take-up portion of the system to allow for splicing by removing these large portions of the belt at the damaged splice. Moreover, it has been found that in high tension applications, the joining device is more likely to fail as the rubber material thereof stretches. With multiple rows of attachment members, the row closest to the belt end sees most of the loading and once it fails, either the joining device will catastrophically fail along that attachment row or the remaining rows of attachment members also begin to fail.
Accordingly, a conveyor belt fastener that reduces the force of impacts of conveyor system components including cleaner blades as well as conveyed material therewith and chatter of the blades along the conveyor belt and damage to the belt would be desired. Further, and as mentioned, the belt fastener preferably minimizes sifting and carry back of material on the belt to areas therebelow while still enabling conveyor belt troughing.